Pattern forming method

ABSTRACT

A near-field exposure mask according to an embodiment includes: a substrate; a concave-convex structure having convexities and concavities and formed on one surface of the substrate; a near-field light generating film arranged at least on a tip portion of each of the convexities, the near-field light generating film being a layer containing at least one element selected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed with layers made of some of those materials; and a resin filled in each of the concavities.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/755,188, filed Jan. 31, 2013, now allowed; and based upon and claimsthe benefit of priority from prior Japanese Patent Application No.2012-081893 filed on Mar. 30, 2012 in Japan, the entire contents ofwhich are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a near-field exposuremask and a pattern forming method.

BACKGROUND

In recent years, there have been increasing demands for devices withhigher densities and higher integration degrees in the fields of variouselectronic devices that require fine processing, such as semiconductordevices. To satisfy those demands, formation of finer patterns of wiringetc. is essential. In procedures for manufacturing such semiconductordevices, the photolithography technology plays an important role in theformation of fine patterns.

Further, there has been a demand for higher-density microfabrication ofsemiconductor packages, interposers, printed circuit boards, and thelike, as semiconductors have been made to have smaller sizes, higherdensities, and higher speeds. Particularly, in recent years, at the timeof formation of a storage media fine structure pattern or formation of abiochip nanostructure, high-density microfabrication is more and morestrongly required. As a mass-production means to satisfy such atechnical demand, the nanoimprint technology has been studied in recentyears.

The nanoimprint technology has been developed by applying a pressingmethod using a metal mold to the nanoscale technology, and involves ananoscale mold processing technique for performing molding by pressing amold with minute concavities and convexities against an object to beprocessed. By the nanoimprint technology, patterns with a width ofseveral tens of nanometers can be formed. Compared with an equivalentprocessing technology using an electron beam, the nanoimprint technologyhas the advantage that a large number of patterns can be molded at verylow costs.

In the nanoimprint technology, the use of near-field light has beensuggested. Generally, in the nanoimprint technology, a mold withconcavities and convexities is pressed against a substrate, on which alight-curable resin is applied, and exposed to ultraviolet to cure thelight-curable resin. Since the mold that is pressed against thelight-curable resin is exposed to ultraviolet, there is a problem inthat the mold releasability is low when the mold is removed from theresin after it is exposed to ultraviolet.

Furthermore, it is required to improve the adhesion between the templateand the substrate when transferring the ultrafine pattern. Thus, itcannot be said that a sufficient study has been performed in theoptimization of pattern forming method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a firstembodiment.

FIGS. 2A through 2D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to the firstembodiment.

FIGS. 3A through 3D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a secondembodiment.

FIGS. 4A through 4D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to the secondembodiment.

FIGS. 5A through 5D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a thirdembodiment.

FIGS. 6A through 6D are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to the thirdembodiment.

FIGS. 7A through 7F are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a fourthembodiment.

FIGS. 8A through 8F are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a fifthembodiment.

FIGS. 9A through 9F are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a sixembodiment.

FIGS. 10A through 10F are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to a seventhembodiment.

FIGS. 11A through 11F are cross-sectional views illustrating a procedureof manufacturing a near-field exposure mask according to an eighthembodiment.

FIG. 12 is a cross-sectional view for explaining a near-field opticallithography method according to a ninth embodiment.

FIGS. 13A and 13B are cross-sectional views for explaining a method offorming a near-field light generating film of a near-field exposure maskaccording to the fifth to the eighth embodiments.

FIGS. 14A and 14B are cross-sectional views illustrating a near-fieldexposure apparatus according to a tenth embodiment.

FIGS. 15A through 15D are cross-sectional views for explaining a patternforming method according to an eleventh embodiment.

FIGS. 16A through 16D are cross-sectional views illustrating a resistpattern forming method and a device manufacturing method according to atwelfth embodiment.

FIGS. 17A through 17E are cross-sectional views for explaining a patternforming method according to a thirteenth embodiment.

FIGS. 18A through 18C are cross-sectional views for explaining thepattern forming method according to the thirteenth embodiment.

DETAILED DESCRIPTION

A near-field exposure mask according to an embodiment includes: asubstrate; a concave-convex structure having convexities and concavitiesand formed on one surface of the substrate; a near-field lightgenerating film arranged at least on a tip portion of each of theconvexities, the near-field light generating film being a layercontaining at least one element selected from the group consisting ofAu, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a filmstack formed with layers made of some of those materials; and a resinfilled in each of the concavities.

The following is a description of embodiments, with references to theaccompanying drawings.

First Embodiment

Referring to FIGS. 1A through 2D, a near-field exposure mask(hereinafter also referred to as “near-field generating member”)according to a first embodiment is described. FIGS. 1A through 2D arecross-sectional views illustrating the procedures for manufacturing thenear-field exposure mask according to the first embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 1A and 1B). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or an Extreme Ultra-Violet (EUV) lithography technique (FIG.1C). This resist pattern 4 a is a line-and-space pattern in which theline width W₁ is 10 nm, and the space width W₂ is 10 nm, for example.Accordingly, the height of the resist pattern 4 a is 10 nm to 30 nm.

After that, a near-field light generating film 6 is deposited on theresist pattern 4 a, to fill the spaces in the resist pattern 4 a (FIG.1D). The near-field light generating film 6 may be a layer containing atleast one element selected from the group consisting of Au, Al, Ag, Cu,Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formedwith layers made of some of those materials.

By using Chemical Mechanical Polishing (CMP), the near-field lightgenerating film 6 is polished, and the upper surface of the resistpattern 4 a is exposed (FIG. 2A). As a result, a near-field lightgenerating film pattern 6 a, which is obtained by filling the near-fieldlight generating film in concavities of the resist pattern 4 a on thesilicon substrate 2, is formed (FIG. 2A). Thereafter, the resist pattern4 a is removed by using resist remover. In this manner, the near-fieldlight generating film 6 a having concavities and convexities is left onthe silicon substrate 2. The near-field light generating film pattern 6a is a line-and-space pattern in which the line width W₂ is 10 nm, andthe space width W₁ is 10 nm. Accordingly, the height (the thickness) ofthe lines in the near-field light generating film pattern 6 a is 10 nmto 30 nm. The height (the thickness) of the lines in the near-fieldlight generating film pattern 6 a is 100 nm or smaller so thatnear-field light reaches the resist to be exposed, but is preferably 50nm or smaller. Alternatively, the near-field light generating filmpattern 6 a may be a pattern in which the line width W₂ is 5 nm orgreater, and the space width W₁ is 5 nm or greater. It should be notedthat the preferred sizes in the near-field light generating film pattern6 a vary with devices to be formed by using the near-field exposuremask.

Then, a thermosetting resin 7, for example silicon resin, is depositedon the silicon substrate, on which the near-field light generating filmpattern 6 a is formed, by a potting method, for example, and cured by aheating process at a temperature of 150° C. (FIG. 2C). The method offorming the thermosetting resin 7 is not limited to the potting method,but can be any other method. Thereafter, the thermosetting resin 7 ispolished by using CMP to expose the upper surface of the near-fieldlight generating film pattern 6 a, thereby forming a near-field exposuremask 1 (FIG. 2D).

The near-field exposure mask 1 thus formed includes a near-field lightgenerating film pattern 6 a with concavities and convexities formed onthe silicon substrate 2, and a resin 7 a filled in the concavities ofthe near-field light generating film pattern. Accordingly, if thenear-field exposure mask 1 of this embodiment is pressed against alight-curable resin which is formed on a substrate and on which apattern has been transferred, and exposed to a light to perform ananoimprint process by means of a near-field light, it is possible toprevent the light-curable resin from being filled into the concavitiesof the near-field light generating film pattern 6 a. Incidentally, amaterial with a high mold releasability is selected for thelight-curable resin to be formed on the substrate, on which a pattern istransferred, and the resin 7 a to be filled into the concavities of thenear-field light generating film pattern. As a result, using thenear-field exposure mask 1, it is possible to prevent the degradation ofthe resolution of the pattern to be transferred even if the nanoimprintprocess is repeatedly performed.

A silicon resin, an epoxy resin, and so on can be used as thethermosetting resin. Furthermore, instead of a thermosetting resin, alight-curable resin can be used.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As described above, according to this embodiment, it is possible toprovide a pattern forming method by which it is possible to transfer anultrafine pattern onto a substrate with a high accuracy.

In this embodiment, the near-field exposure mask 1 is formed with thesilicon substrate 2, the near-field light generating film pattern 6 a,and the resin 7 a. Accordingly, the durability can be increased, and thenear-field exposure mask 1 can be formed through simple manufacturingprocedures.

Second Embodiment

Referring now to FIGS. 3A though 4D, a near-field exposure maskaccording to a second embodiment is described. FIGS. 3A though 4D arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the second embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 3A and 3B). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or an EUV lithography technique (FIG. 3C). This resist pattern4 a is a line-and-space pattern in which the line width W₁ is 10 nm, andthe space width W₂ is 10 nm, for example. Accordingly, the height of theresist pattern 4 a is 10 nm to 30 nm. Thereafter, the silicon substrate2 is etched by means of Reactive Ion Etching (RIE) using the resistpattern 4 a as a mask (FIG. 3D). As a result, a silicon substrate 2 ahaving a pattern of concavities and convexities on its surface isobtained (FIG. 3D). The pattern of concavities and convexities of thesilicon substrate 2 a is a line-and-space pattern in which the linewidth is W₂ and the space width is W₂.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 4A). A near-field lightgenerating film 6 is deposited on at least a top surface (tip portion)and sides of each of the convexities of the pattern of concavities andconvexities of the silicon substrate 2 a (FIG. 4B). Although it is notshown in the drawings, the near-field light generating film 6 can alsobe deposited on the bottoms of the concavities. The near-field lightgenerating film 6 may be a layer containing at least one elementselected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In,Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed with layers made ofsome of those materials. Furthermore, the thickness of the near-fieldlight generating film 6 on the tip portion is from 2 nm to 80 nm, andpreferably, from 5 nm to 40 nm.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and Molecular Beam Epitaxy (MBE), but thedeposition method to be used here is not limited thereto. By adjustingthe irradiation angle relative to the direction of the irradiationsource, it is possible to adjust the thickness or thickness ratio of thenear-field light generating film 6 to be formed on the top surface andthe sides of each of the concavities.

Then, a thermosetting resin 7, for example silicon resin, is depositedon an upper surface of the substrate 2, on which the near-field lightgenerating film 6 is formed, by a potting method, for example, and curedby a heating process at a temperature of 150° C. (FIG. 4C). The methodof depositing the thermosetting resin is not limited to the pottingmethod, but can be any other method. Thereafter, the thermosetting resin7 is polished by CMP to expose the upper surface of the near-field lightgenerating film 6, thereby forming a near-field exposure mask 1 (FIG.4D).

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on at least the top surface and the sides ofeach of the convexities of the pattern of concavities and convexitiesformed on the surface of the silicon substrate, and a resin 7 a isfilled in the concavities of the pattern of concavities and convexities.Accordingly, if the near-field exposure mask 1 of this embodiment ispressed against a light-curable resin which is formed on a substrate andon which a pattern has been transferred, and exposed to a light toperform a nanoimprint process by means of a near-field light, it ispossible to prevent the light-curable resin from being filled into theconcavities of the pattern of concavities and convexities. Incidentally,a material with a high mold releasability is selected for thelight-curable resin to be formed on the substrate, on which a pattern istransferred, and the resin 7 a to be filled into the concavities of thenear-field light generating film pattern. As a result, using thenear-field exposure mask 1, it is possible to prevent the degradation ofthe resolution of the pattern to be transferred even if the nanoimprintprocess is repeatedly performed.

A silicon resin, an epoxy resin, and so on can be used as thethermosetting resin. Furthermore, instead of a thermosetting resin, alight-curable resin can be used.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As described above, according to this embodiment, it is possible toprovide a pattern forming method by which it is possible to transfer anultrafine pattern onto a substrate with a high accuracy.

In this embodiment, the near-field exposure mask 1 is formed with thesilicon substrate 2 a, the near-field light generating film pattern 6 a,and the resin 7 a. Accordingly, the durability can be increased, and thenear-field exposure mask 1 can be formed through simple manufacturingprocedures.

Third Embodiment

Referring now to FIGS. 5A though 6D, a near-field exposure maskaccording to a third embodiment is described. FIGS. 5A though 6D arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the third embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 5A and 5B). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or EUV lithography technique (FIG. 5C). This resist pattern 4a is a line-and-space pattern in which the line width W₁ is 10 nm, andthe space width W₂ is 10 nm, for example. Accordingly, the height of theresist pattern 4 a is 10 nm to 30 nm. Thereafter, the silicon substrate2 is etched by means of RIE using the resist pattern 4 a as a mask (FIG.5C). As a result, a silicon substrate 2 a having a pattern ofconcavities and convexities on its surface can be obtained (FIG. 5D).The pattern of concavities and convexities of the silicon substrate 2 ais a line-and-space pattern in which the line width is W₂ and the spacewidth is W₁.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 6A). A near-field lightgenerating film 6 is deposited on a top surface and part of sidesconnecting to the top surface of each of the convexities of the patternof concavities and convexities of the silicon substrate 2 a (FIG. 6B).The near-field light generating film 6 may be a layer containing atleast one element selected from the group consisting of Au, Al, Ag, Cu,Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formedwith layers made of some of those materials.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and MBE, but the deposition method to be usedhere is not limited thereto. By adjusting the irradiation angle relativeto the direction of the irradiation source, it is possible to adjust thethickness or thickness ratio of the near-field light generating film 6to be formed on the top surface and the sides of each of theconcavities.

Then, a thermosetting resin 7, for example silicon resin, is depositedon an upper surface of the substrate 2, on which the near-field lightgenerating film pattern 6 is formed, by a potting method, for example,and cured by a heating process at a temperature of 150° C. (FIG. 6C).The method of depositing the thermosetting resin is not limited to thepotting method, but can be any other method. Thereafter, thethermosetting resin 7 is polished by CMP to expose the upper surface ofthe near-field light generating film 6, thereby forming a near-fieldexposure mask 1 (FIG. 6D).

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on at least the top surface and part of thesides connecting to the top surface of each of the convexities of thepattern of concavities and convexities formed on the surface of thesilicon substrate, and a resin 7 a is filled in the concavities of thepattern of concavities and convexities. Accordingly, if the near-fieldexposure mask 1 of this embodiment is pressed against a light-curableresin which is formed on a substrate and on which a pattern has beentransferred, and exposed to a light to perform a nanoimprint process bymeans of a near-field light, it is possible to prevent the light-curableresin from being filled into the concavities of the pattern ofconcavities and convexities. Incidentally, a material with a high moldreleasability is selected for the light-curable resin to be formed onthe substrate, on which a pattern is transferred, and the resin 7 a tobe filled into the concavities of the near-field light generating filmpattern. As a result, using the near-field exposure mask 1, it ispossible to prevent the degradation of the resolution of the pattern tobe transferred even if the nanoimprint process is repeatedly performed.

A silicon resin, an epoxy resin, and so on can be used as thethermosetting resin. Furthermore, instead of a thermosetting resin, alight-curable resin can be used.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As described above, according to this embodiment, it is possible toprovide a pattern forming method by which it is possible to transfer anultrafine pattern onto a substrate with a high accuracy.

In this embodiment, the near-field exposure mask 1 is formed with thesilicon substrate 2 a, the near-field light generating film pattern 6 a,and the resin 7 a. Accordingly, the durability can be increased, and thenear-field exposure mask 1 can be formed through simple manufacturingprocedures.

Fourth Embodiment

Referring now to FIGS. 7A though 7F, a near-field exposure maskaccording to a fourth embodiment is described. FIGS. 7A though 7F arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the fourth embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 7A and 7A). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or EUV lithography technique (FIG. 7C). This resist pattern 4a is a line-and-space pattern in which the line width W₁ is 10 nm, andthe space width W₂ is 10 nm, for example. Accordingly, the height of theresist pattern 4 a is 10 nm to 30 nm. Thereafter, a near-field lightgenerating film 6 is deposited on the resist pattern 4 a so as to fillthe spaces (concavities) of the resist pattern 4 a (FIG. 7D). Thenear-field light generating film 6 may be a layer containing at leastone element selected from the group consisting of Au, Al, Ag, Cu, Cr,Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed withlayers made of some of those materials.

Thereafter, the near-field light generating film 6 is polished by usingCMP to expose the upper surface of the resist pattern 4 a, therebyleaving a near-field light generating film 6 a in the spaces(concavities) of the resist pattern 4 a (FIG. 7E).

Then, the resist pattern 4 a is removed using a resist removing agent toform a near-field exposure mask 1 (FIG. 7F). As a result, aline-and-space pattern, which is formed of the near-field lightgenerating film 6 a, and in which the width of the lines (convexities)is W₂ and the width of the spaces (concavities) is W₁, is formed on thesilicon substrate 2.

In the near-field exposure mask 1 thus formed, a pattern of concavitiesand convexities formed of the near-field light generating film 6 isformed on the silicon substrate.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As will be described later in the descriptions of the ninth embodiment,according to this embodiment, it is possible to provide a patternforming method by which it is possible to transfer an ultrafine patternonto a substrate with a high accuracy.

In this embodiment, the near-field exposure mask 1 is formed of thesilicon substrate 2 and the near-field light generating film 6 a.Accordingly, the durability can be increased, and the near-fieldexposure mask 1 can be formed through simple manufacturing procedures.

Fifth Embodiment

Referring now to FIGS. 8A though 8F, a near-field exposure maskaccording to a fifth embodiment is described. FIGS. 8A though 8F arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the fifth embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 8A and 8B). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or EUV lithography technique (FIG. 8C). This resist pattern 4a is a line-and-space pattern in which the line width W₁ is 10 nm, andthe space width W₂ is 10 nm, for example. Accordingly, the height of theresist pattern 4 a is 10 nm to 30 nm. Thereafter, the silicon substrate2 is etched by means of RIE using the resist pattern 4 a as a mask (FIG.8D). As a result, a silicon substrate 2 a having a pattern ofconcavities and convexities on its surface can be obtained (FIG. 8D).The pattern of concavities and convexities of the silicon substrate 2 ais a line-and-space pattern in which the line width is W₂ and the spacewidth is W₁.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 8E). A near-field lightgenerating film 6 is deposited on a top surface of each of theconvexities and a bottom of each of the concavities of the pattern ofconcavities and convexities of the silicon substrate 2 a (FIG. 8F). Thenear-field light generating film 6 may be a layer containing at leastone element selected from the group consisting of Au, Al, Ag, Cu, Cr,Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed withlayers made of some of those materials.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and MBE, but the deposition method to be usedhere is not limited thereto. By adjusting the irradiation angle relativeto the direction of the irradiation source, it is possible to adjust thethickness or thickness ratio of the near-field light generating film 6to be formed on the top surface of each of the convexities and thebottom of each of the concavities.

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on the top surface of each of theconvexities and the bottom of each of the concavities of the pattern ofconcavities and convexities formed on the surface of the siliconsubstrate.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As will be described later in the descriptions of the ninth embodiment,according to this embodiment, it is possible to provide a patternforming method by which it is possible to transfer an ultrafine patternonto a substrate with a high accuracy.

Furthermore, in this embodiment, the near-field exposure mask 1 isformed of the silicon substrate 2 a and the near-field light generatingfilm 6. Accordingly, the durability can be increased, and the near-fieldexposure mask 1 can be formed through simple manufacturing procedures.

Six Embodiment

Referring now to FIGS. 9A though 9F, a near-field exposure maskaccording to a sixth embodiment is described. FIGS. 9A though 9F arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the sixth embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 9A and 9B). A resist pattern 4 a isthen formed in the resist layer 4 by using an electron beam lithographytechnique or EUV lithography technique (FIG. 9C). This resist pattern 4a is a line-and-space pattern in which the line width W₁ is 10 nm, andthe space width W₂ is 10 nm, for example. Accordingly, the height of theresist pattern 4 a is 10 nm to 30 nm. Thereafter, the silicon substrate2 is etched by means of RIE using the resist pattern 4 a as a mask (FIG.9D). As a result, a silicon substrate 2 a having a pattern ofconcavities and convexities on its surface can be obtained (FIG. 9D).The pattern of concavities and convexities of the silicon substrate 2 ais a line-and-space pattern in which the line width is W₂ and the spacewidth is W₁.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 9E). A near-field lightgenerating film 6 is deposited on a top surface of each of theconvexities, sides connecting the top surface of each convexities, and abottom of each of the concavities of the pattern of concavities andconvexities of the silicon substrate 2 a (FIG. 9F). The near-field lightgenerating film 6 may be a layer containing at least one elementselected from the group consisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In,Ge, Sn, Pb, Zn, Pd, and C, or a film stack formed with layers made ofsome of those materials.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and MBE, but the deposition method to be usedhere is not limited thereto. By adjusting the irradiation angle relativeto the direction of the irradiation source, it is possible to adjust thethickness or thickness ratio of the near-field light generating film 6to be formed on the top surface of each of the convexities, the sidesconnecting the top surface of each of the convexities, and the bottom ofeach of the concavities of the pattern of concavities and convexities.

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on the top surface of each of theconvexities, the sides connecting the top surface of each of theconvexities, and the bottom of each of the concavities of the pattern ofconcavities and convexities formed on the surface of the siliconsubstrate.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As will be described later in the descriptions of the ninth embodiment,according to this embodiment, it is possible to provide a patternforming method by which it is possible to transfer an ultrafine patternonto a substrate with a high accuracy.

Furthermore, in this embodiment, the near-field exposure mask 1 isformed of the silicon substrate 2 a and the near-field light generatingfilm 6. Accordingly, the durability can be increased, and the near-fieldexposure mask 1 can be formed through simple manufacturing procedures.

Seventh Embodiment

Referring now to FIGS. 10A though 10F, a near-field exposure maskaccording to a seventh embodiment is described. FIGS. 10A though 10F arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the seventh embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 10A and 10B). A resist pattern 4 ais then formed in the resist layer 4 by using an electron beamlithography technique or EUV lithography technique (FIG. 10C). Thisresist pattern 4 a is a line-and-space pattern in which the line widthW₁ is 10 nm, and the space width W₂ is 10 nm, for example. Accordingly,the height of the resist pattern 4 a is 10 nm to 30 nm.

Thereafter, the silicon substrate 2 is etched by means of RIE using theresist pattern 4 a as a mask (FIG. 10D). As a result, a siliconsubstrate 2 a having a pattern of concavities and convexities on itssurface can be obtained (FIG. 10D). The pattern of concavities andconvexities of the silicon substrate 2 a is a line-and-space pattern inwhich the line width is W₁ and the space width is W₂.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 10E). A near-field lightgenerating film 6 is deposited on a top surface and sides of each of theconvexities of the pattern of concavities and convexities of the siliconsubstrate 2 a (FIG. 10F). The near-field light generating film 6 may bea layer containing at least one element selected from the groupconsisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, andC, or a film stack formed with layers made of some of those materials.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and MBE, but the deposition method to be usedhere is not limited thereto. By adjusting the irradiation angle relativeto the direction of the irradiation source, it is possible to adjust thethickness or thickness ratio of the near-field light generating film 6to be formed on the top surface and the sides of each of the convexitiesof the pattern of concavities and convexities.

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on the top surface and the sides of each ofthe convexities of the pattern of concavities and convexities formed onthe surface of the silicon substrate.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As will be described later in the descriptions of the ninth embodiment,according to this embodiment, it is possible to provide a patternforming method by which it is possible to transfer an ultrafine patternonto a substrate with a high accuracy.

Furthermore, in this embodiment, the near-field exposure mask 1 isformed of the silicon substrate 2 a and the near-field light generatingfilm 6. Accordingly, the durability can be increased, and the near-fieldexposure mask 1 can be formed through simple manufacturing procedures.

Eighth Embodiment

Referring now to FIGS. 11A though 11F, a near-field exposure maskaccording to an eighth embodiment is described. FIGS. 11A though 11F arecross-sectional views illustrating a procedure of manufacturing anear-field exposure mask according to the eighth embodiment.

First, a silicon substrate 2 of 600 μm in thickness is prepared, and aresist layer 4 of 10 nm to 30 nm in thickness, for example, is appliedonto the silicon substrate 2 (FIGS. 11A and 11B). A resist pattern 4 ais then formed in the resist layer 4 by using an electron beamlithography technique or EUV lithography technique (FIG. 11C). Thisresist pattern 4 a is a line-and-space pattern in which the line widthW₁ is 10 nm, and the space width W₂ is 10 nm, for example. Accordingly,the height of the resist pattern 4 a is 10 nm to 30 nm.

Thereafter, the silicon substrate 2 is etched by means of RIE using theresist pattern 4 a as a mask (FIG. 11D). As a result, a siliconsubstrate 2 a having a pattern of concavities and convexities on itssurface can be obtained (FIG. 11D). The pattern of concavities andconvexities of the silicon substrate 2 a is a line-and-space pattern inwhich the line width is W₂ and the space width is W₁.

By removing the resist pattern 4 a, it is possible to obtain a siliconsubstrate 2 a with an ultrafine pattern (FIG. 11E). A near-field lightgenerating film 6 is deposited on a top surface of each of theconvexities and sides connecting the top surface of each of theconvexities of the pattern of concavities and convexities of the siliconsubstrate 2 a (FIG. 11F). The near-field light generating film 6 may bea layer containing at least one element selected from the groupconsisting of Au, Al, Ag, Cu, Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, andC, or a film stack formed with layers made of some of those materials.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions. Typical deposition methods are vapordeposition, sputtering, and MBE, but the deposition method to be usedhere is not limited thereto. By adjusting the irradiation angle relativeto the direction of the irradiation source, it is possible to adjust thethickness or thickness ratio of the near-field light generating film 6to be formed on the top surface and the sides of each of the convexitiesof the pattern of concavities and convexities.

In the near-field exposure mask 1 thus formed, a near-field lightgenerating film 6 is formed on the top surface and the sides of each ofthe convexities of the pattern of concavities and convexities formed onthe surface of the silicon substrate.

As the substrate, a glass substrate can be used in addition to thesilicon substrate.

As will be described later in the descriptions of the ninth embodiment,according to this embodiment, it is possible to provide a patternforming method by which it is possible to transfer an ultrafine patternonto a substrate with a high accuracy.

Furthermore, in this embodiment, the near-field exposure mask 1 isformed of the silicon substrate 2 a and the near-field light generatingfilm 6. Accordingly, the durability can be increased, and the near-fieldexposure mask 1 can be formed through simple manufacturing procedures.

Ninth Embodiment

Referring now to FIG. 12, a near-field optical lithography methodaccording to a ninth embodiment is described.

A near-field exposure method and a near-field optical nanoimprint methodare lithography techniques involving near-field light generating membersas masks, and are designed for generating near-field light from lighthaving a longer wavelength than the wavelength of propagating light thatis normally emitted. It is known that, with the use of near-field light,a photochemical reaction occurs in the resist at a shorter wavelength atwhich a reaction does not normally occur. Accordingly, no reactionsoccur at portions irradiated only with propagating light from whichnear-field light is not generated, but a photochemical reaction occursonly at the portions where near-field light exists, to enablepatterning. This is a phenomenon that occurs both in the case of anear-field exposure method and in the case of a near-field opticalnanoimprint method.

Near-field light with high intensity is focused locally onto portionswith small radii of curvature in the surface. That is, the electricalfield intensity of near-field light tends to become higher at portionsnear the corners. Therefore, in a light exposure using nanoimprint or amask, patterning is performed depending on the line shapes of the mask.However, if an exposure or imprint curing occurs only at both sides ofthe mask in the mask width direction, the patterned linewidth becomessmaller by half or more, and the number of lines is doubled. That is,with the use of near-field light, finer patterning can be performed.

The near-field optical lithography method according to the ninthembodiment uses the near-field exposure mask 1 of any of the firstthrough eights embodiments as a near-field exposure mask (near-fieldlight generating member). In FIG. 12, the near-field exposure maskaccording to the sixth embodiment shown in FIG. 9F is used. As shown inFIG. 12, in a near-field light generating member 100, at least oneconvex portion 104 is formed on one of the facing surfaces of atransparent substrate 102. The substrate 102 and the convex portion 104can be made of different materials from each other, or may be made ofthe same material. Examples of materials of the respective substratesinclude Si, SiO₂, sapphire, magnesium fluoride, zinc sulfide, zincselenide, and calcium fluoride. The convex portion 104 includes a topend 104 a and sides 104 b. The sides 104 b are side faces that connectthe top end 104 a and the substrate 102. The top end 104 a and the sides104 b are covered with a near-field light generating layer 106 that ismade of metal, CNT (carbon nanotube), or graphene. Specifically, thenear-field light generating layer 106 includes a first layer 106 acovering the top end 104 a of the convex portion 104, and a second layer106 b covering the sides 104 b of the convex portion 104. Further, athird layer 106 c made of metal, CNT (carbon nanotube), or graphene canbe or may not be formed in the region other than the convex portion 104on the surface of the substrate 102 on which the convex portion 104 isformed.

The near-field light generating member 100 and a substrate 120, on whicha light-curable resin layer 122 is formed, are positioned so that andthe light-curable resin layer 122 faces the convex portion 104. In thissituation, light is emitted onto the back surface of the near-fieldlight generating member 100, or onto the surface on the opposite sidefrom the surface on which the convex portion 104 is formed. In thismanner, near-field light is generated from the near-field lightgenerating layer 106, and the photosensitive resin layer 122 is exposedby the near-field light. If the substrate 120 is a transparentsubstrate, light can be emitted onto the substrate 120.

In order to deposit the near-field light generating film 6, thedirection of the irradiation source is set to be diagonal relative toplane of the substrate, and the deposition is performed from both theright and left directions, as shown in FIGS. 13A and 13B. Typicaldeposition methods are vapor deposition, sputtering and MBE, but thedeposition method to be used here is not limited thereto. By adjustingthe irradiation angle relative to the direction of the irradiationsource, it is possible to adjust the thickness or thickness ratio ofeach of the first layer 106 a, the second layer 106 b, and the thirdlayer 106 c.

Metal, CNT (carbon nanotube), and graphene has the function to generateand guide near-field light. Near-field light generated by any of thosematerials has excellent polarization components in the travelingdirection (the direction from the substrate toward the top end of theconvex portion in the side faces of the convex portion) or has excellentso-called z-polarized light (light polarized in the travelingdirection), compared with the polarization components of general planewave propagation light that are perpendicular to the travelingdirection. Therefore, the near-field light is suitable for the use inthe lithography technology, and has double patterning properties.Accordingly, stronger double patterning can be performed, if a resistformed by the lithography technology or the polymerization initiator ofa curable resin in a nanoimprint method strongly reacts to z-polarizedlight.

Further, by reducing the width of the convex portion, fine patterning,if not double patterning, can be performed.

As described above, according to this embodiment, it is possible toprovide a pattern forming method by which it is possible to transfer anultrafine pattern onto a substrate with a high accuracy.

Tenth Embodiment

Referring now to FIGS. 14A and 14B, a near-field exposure apparatusaccording to a tenth embodiment is described. A near-field exposureapparatus 20 of the tenth embodiment performs exposures, using thenear-field exposure mask 1 of the fourth embodiment shown in FIG. 7, forexample. The near-field exposure apparatus 20 includes: a mount table 22a on which a to-be-processed substrate 12 having a resist 14 appliedthereto is placed, a supporting table 22 b that supports the face of thenear-field exposure mask 1 on which the near-field light generating filmpattern 6 a is formed; and a mask 24 to allow light from a light source26 to irradiate the region of the near-field exposure mask 1 on whichthe near-field light generating film pattern 6 a is formed. As shown inFIGS. 14A and 14B, light is emitted from the light source 26 located onthe side where there is the silicon substrate 2 of the near-fieldexposure mask 1, and the near-field light generating film pattern 6 aand the resist 14 applied onto the to-be-exposed substrate 12 arepositioned to face each other. Incidentally, the near-filed exposureapparatus 20 of the tenth embodiment may be exposed to light using thenear-field exposure mask 1 of any of the first to the third embodiments,or the near-field exposure mask 1 of any of the fifth to the eighthsembodiments.

FIG. 14A is a cross-sectional view showing a situation where thenear-field light generating film pattern 6 a of the near-field exposuremask 1 is not in contact with the resist 14 applied onto theto-be-processed substrate 12. FIG. 14B is a cross-sectional view showinga situation where the near-field light generating film pattern 6 a ofthe near-field exposure mask is in contact with the resist 14 appliedonto the to-be-processed substrate 12.

The near-field exposure apparatus 20 of the tenth embodiment includesthe light source 26 used for near-field exposures, and a positiondetermining mechanism 28. The position determining mechanism 28 moveseither of the near-field exposure mask 1 and the to-be-processedsubstrate 12, onto which the resist 14 is applied, for determining theposition thereof so that the upper surface of the near-field lightgenerating film pattern 6 a of the near-field exposure mask 1 and thesurface of the resist 14 applied onto the to-be-processed substrate 12are “in contact with” each other. The position determining mechanism 28id driven by, for example, a vacuum pump or the like.

The feature herein that the upper surface of the near-field lightgenerating film pattern 6 a and the surface of the resist 14 appliedonto the to-be-processed substrate 12 are “in contact with” each othermeans that they are in a range where the effect of near-field lightreaches (for example, in a range of −10 nm or more to less than 0 nm, ormore than 0 nm to 10 nm or less). Thus, the upper surface of thenear-field light generating film pattern 6 a and the surface of theresist 14 are not necessarily in contact with each other actually. Thatis, if the distance between the upper surface of the near-field lightgenerating film pattern 6 a and the surface of the resist 14 appliedonto the to-be-processed substrate 12 is in a range of −10 nm or more toless than 0 nm or more than 0 nm to 10 nm or less, the effect ofnear-field light reaches thereto, resulting in that it is possible totransfer a ultrafine pattern onto the substrate accurately. Herein, aminus distance means that upper surface of the near-field lightgenerating film pattern 6 a sinks into the surface of the resist 14.

When the near-field light generating film pattern 6 a is not in contactwith the resist 14 applied onto the to-be-processed substrate 12 asshown in FIG. 14A, the position determining mechanism 28 does notoperate, and the light source 26 is in an OFF state. On the other hand,when the near-field light generating film pattern 6 a is in contact withthe resist 14 applied onto the to-be-processed substrate 12 as shown inFIG. 14B, the position determining mechanism 28 operates, and the lightsource 26 is in an ON state. That is, by activating the positiondetermining mechanism 28, the near-field light generating film pattern 6a is brought into contact with the resist 14. With the near-field lightgenerating film pattern 6 a being in contact with the resist 14, theback surface of the near-field exposure mask 1 is irradiated with thelight from the light source 26. It should be noted that the light source26 needs to be a light source that generates light of 1100 nm or longerin wavelength, because light of 1100 nm or longer in wavelength can passthrough Si.

As a result, near-field light is generated from the opening portions ofthe near-field light generating film pattern 6 a of the near-fieldexposure mask 1, and a pattern latent image is transferred to the resist14 on the to-be-processed substrate 12. The exposure is preferablyperformed where the near-field exposure mask 1 and the resist 14 formedon the to-be-processed substrate 12 are in good contact with each other(without any non-contact region) in the area in which the pattern is tobe formed. In the tenth embodiment, exposures are performed with lightentering from the opposite side from the side on which the near-fieldlight generating film pattern 6 a of the near-field exposure mask 1 isformed. However, as will be described later, exposures may be performedwith light entering from the side on which the near-field lightgenerating film pattern 6 a of the near-field exposure mask 1 is formed.

In this manner, it is possible to transfer a ultrafine pattern onto theto-be-processed substrate 12 accurately by exposing the resist 14 tonear-field light, developing the resist 14 thus exposed to form a resistpattern, and etching the to-be-processed substrate 12 using this resistpattern as a mask.

As the resist 14 used in the tenth embodiment, either a positive resistor negative resist can be used. Examples of positive resists that can beused include a diazonaphthoquinone-novolac resist and achemically-amplified positive resist. Examples of negative resists thatcan be used include a chemically-amplified negative resist, a photocation polymerizable resist, a photo radical polymerizable resist, apolyhydroxystyrene-bisazide resist, a cyclized rubber-bisazide resist,and a polyvinyl cinnamate resist. With the use of a chemically-amplifiedpositive resist and a chemically-amplified negative resist, a patternwith a low line edge roughness is formed. Accordingly, the use of achemically-amplified positive resist or chemically-amplified negativeresist is particularly preferable in this embodiment.

In this embodiment, a known light source can be used as the near-fieldlight source 26. For example, a laser having a wavelength of 0.35 μm to20 μm or light-emitting diode can be used. One or more such lightsources can be used. Since semiconductor lasers are less expensive havehigher power, the use of a semiconductor laser or light-emitting diodeis more preferable in this embodiment.

As described above, it is possible to accurately transfer a ultrafinepattern onto a substrate by performing exposure using the near-fieldexposure apparatus of this embodiment to form the pattern.

Eleventh Embodiment

The ninth embodiment is a pattern forming method in which the light isemitted onto the back surface of the near-field exposure mask 100 (ontothe surface of the Si substrate 102 on the opposite side from thesurface on which the near-field light generating film pattern isformed). However, a near-field exposure method according to an eleventhembodiment is a pattern forming method in which light is emitted onto afront surface of the near-field exposure mask 1, or onto the surface onwhich the near-field light generating film pattern 6 a is formed. Theeleventh embodiment is described referring to FIGS. 15A though 15D.

As in the case of the ninth embodiment, a resist layer 54 is appliedonto a Si substrate 52 by a spin coating method or the like, as shown inFIG. 15A. Subsequently, as shown in FIG. 15A, a near-field exposure mask61, in which a near-field light generating film pattern 66 a is formedon a Si substrate 62, is prepared. The near-field exposure mask 61 hasthe same structure as the fourth embodiment.

Then, as shown in FIG. 15B, the positioning is performed so that thenear-field light generating film pattern 66 a is in contact with thesurface of the resist layer 54. Then, light of 1550 nm in wavelength isemitted from the side of Si substrate 52, on the opposite side of whichthe resist is applied. The incident light is p-polarized. Furthermore,the light is incident with a diagonal angle of θi. Although the lightpropagates through the resist layer 54, the resist is not sensitive tothe light since the wavelength used for the light is far longer than thewavelength to which the resist is sensitive. However, the light reachingthe interface between the near-field light generating film pattern 66 aof the near-field exposure mask 61 and the resist layer 54 is convertedto a near-field light 69 at the edge portion of the near-field lightgenerating film pattern 66 a. A resist portion 54 a in the vicinity ofthe region where the near-field light 69 is generated is dissociatedthrough a procedure of multiple-stage transition. Thus, even if light isemitted from the front side of the near-field exposure mask 61, it ispossible to form an ultrafine pattern.

An LED with a wavelength of 1550 nm is used as an exposing light sourceto perform an exposure process with an incident power of 30 mW for twohours. The Si substrate 52 including the resist layer 54 thus exposed isdeveloped by being soaked in a developer for 30 seconds, cleaned by purewater, and cleared of water by means of air blow. The exposed resistportion 54 a is dissolved into the developer, thereby forming a patterncorresponding to the edge portion of the near-field light generatingfilm pattern 66 a. In this manner, it is possible to form a pattern of50 nm in width and 50 nm in depth along the edge portion of thenear-field light generating film pattern 66 a.

Thus, it is possible to transfer an ultrafine pattern onto the substrateto be processed 52 by exposing the resist 54 to near-field light,developing the resist 54 thus exposed to form a resist pattern, andetching the substrate to be processed 52 using the resist pattern as amask.

Furthermore, when light is emitted from the front side of the near-fieldexposure mask 61 as in the eleventh embodiment, the near-field light isexcited more easily in the edge portion of the near-field lightgenerating film pattern 66 a of the near-field exposure mask 61 ascompared with the case where light is emitted from the back side of thenear-field exposure mask as in the ninth embodiment. The reason for thisis that when light is emitted from the back side of the near-fieldexposure mask 61, near-field light is generated in the edge portion ofthe near-field light generating film pattern 66 a on the side of the Sisubstrate 62, and then moves to the edge portion of the near-field lightgenerating film pattern 66 a on the side of the resist layer 54, therebysensitizing the resist layer 54. When the near-field light moves fromthe edge portion of the near-field light generating film pattern 66 a onthe side of the Si substrate 62 to the edge portion of the near-fieldlight generating film pattern 66 a on the side of the resist layer 54,part of the near-field light is absorbed by the near-field lightgenerating film pattern 66 a, resulting in that the intensity of thenear-field light decreases. In contrast, when light is emitted from thefront side of the near-field exposure mask 61, the light propagatesthrough the resist layer 54, and then near-field light is generated inthe edge portion of the near-field light generating film pattern 66 a onthe side of the resist layer 54. Accordingly, as compared with the casewhere light is emitted from the back side of the near-field exposuremask 61, no decrease in the intensity of near-field light is caused bythe near-field light generating film pattern 66 a.

As described above, according to this embodiment, it is possible totransfer an ultrafine pattern onto a substrate accurately.

Twelfth Embodiment

Referring now to FIGS. 16A through 16D, a resist pattern forming methodand a device manufacturing method according to a twelfth embodiment aredescribed.

In the twelfth embodiment, the near-field exposure mask of the fourthembodiment and the near-field exposure apparatus 20 of the tenthembodiment are used, for example.

First, the to-be-processed substrate 12 is prepared, and a light-curableresin is applied onto the to-be-processed substrate 12. Thelight-curable resin may be a single layer. In this embodiment, however,the light-curable resin has a double-layer resist structure formed bystacking a resist layer 15 and a light-curable resin layer 16 in thisorder on the to-be-processed substrate 12. After that, theto-be-processed substrate 12 and the near-field exposure mask 1according to the fourth embodiment are placed and arranged on thenear-field exposure apparatus (not shown) according to the tenthembodiment in such a manner that the near-field light generating filmpattern 6 a of the near-field exposure mask 1 faces the resist layer 14on the to-be-processed substrate 12 (FIG. 16A). The near-field lightgenerating film pattern 6 a of the near-field exposure mask 1 and thelight-curable resin layer 14 on the to-be-processed substrate 12 arebrought into contact with each other, and a near-field exposure isperformed. As a result, near-field light leaks along the edge portionsof the near-field light generating film pattern 6 a, to cure thelight-curable resin layer 14. In this embodiment, the resist layer 14 isa double-layer structure. Therefore, the upper light-curable resin layer16 is exposed with the near-field light.

The near-field exposure mask 1 is then detached from the to-be-processedsubstrate 12, and a pattern 16 a is formed on the resist layer 15, asshown in FIG. 16B. With the pattern 16 a being used as a mask,patterning is performed on the resist layer 15 by using a lithographytechnique, to form a resist pattern 15 a (FIG. 16C). As a result, apattern 14 a having a stack structure formed with the resist pattern 15a and the pattern 16 a is formed on the to-be-processed substrate 12(FIG. 16D).

With the pattern 14 a being used as a mask, dry etching or wet etchingis performed. After the mask is removed, a semiconductor processincluding metal vapor deposition, lift-off, and plating is performed onthe to-be-processed substrate 12, to process the to-be-processedsubstrate 12. In this manner, a desired device is formed in theto-be-processed substrate 12.

As the light-curable resin 16 used in this embodiment, a modifiedacrylate resin, a methacrylate resin, a modified epoxy resin, apolyester acrylate resin, an epoxy acrylate resin, an urethane acrylateresin, and so on can be used.

As the resist layer 15 used in this embodiment, either a positive resistor negative resist can be used, as long as it has photosensitivity tothe light source to be used. Examples of positive resists that can beused include a diazonaphthoquinone-novolac resist and achemically-amplified positive resist. Examples of negative resists thatcan be used include a chemically-amplified negative resist, a photocation polymerizable resist, a photo radical polymerizable resist, apolyhydroxystyrene-bisazide resist, a cyclized rubber-bisazide resist,and a polyvinyl cinnamate resist. With the use of a chemically-amplifiedpositive resistor and a chemically-amplified negative resist, a patternwith high linewidth accuracy is formed.

As the to-be-processed substrate 12, various kinds of substrates can beused, such as a semiconductor substrate made of Si, GaAs, InP, or thelike, an insulating substrate made of glass, quartz, BN, or the like, orany of those substrates on which one or more films made of a resist, ametal, an oxide, or a nitride are formed.

The propagation depth of near-field light is normally 100 nm or less. Toform the pattern 14 a of 100 nm or more in height by near-field opticallithography, a resist layer having a multilayer structure is preferablyused. That is, it is preferable to use the resist layer 14 having adouble-layer structure in which the light-curable resin layer 16 havingendurance to oxygen dry etching is applied onto the lower resist layer15 that is applied onto the to-be-processed substrate 12 and can beremoved by dry etching. Alternatively, it is possible to use a resistlayer having a three-layer structure in which an oxygen plasma etchingendurance layer (not shown) is formed on the lower resist layer 15 thatis applied onto the to-be-processed substrate 12 and can be removed bydry etching, and the resist layer 16 is further applied onto the oxygenplasma etching endurance layer.

The applications of the resists 14, 15, and 16 can be performed by usingknown application apparatuses and known methods such as potting, inkjet,a spin coater, a dip coater, and a roller coater, and so on.

The film thicknesses are comprehensively determined by taking intoaccount the processing depth of the to-be-processed substrate 12, andthe plasma etching endurances and light intensity profiles of theresists. Normally, the applications are preferably performed so that thefilm thicknesses fall within the range of 10 nm to 300 nm after prebake.

Further, prior to the applications of the resists 14, 15, and 16, one ormore of the following high-boiling-point solvents may be added to reducethe film thicknesses after the prebake: benzyl ethyl ether, di-n-hexylether, diethylene glycol monomethyl ether, diethylene glycol monoethylether, acetonylacetone, isophorone, capronic acid, caprylic acid,1-octanol, 1-nonanol, benzyl alcohol, benzyl acetate, ethyl benzoate,diethyl oxalate, diethyl maleic acid, γ-butyrolactone, ethylenecarbonate, propylene carbonate, ethylene glycol monophenyl etheracetate, and the like.

After the application, the resist layers are prebaked at 80° C. to 200°C., or more preferably, at 80° C. to 150° C. In the prebake, a heatingmeans such as a hot plate or a hot air drying machine can be used.

After the near-field exposure, the mask 1 is detached from theto-be-processed substrate 12, thereby forming a near-field resistpattern. When the resist pattern 16 a formed through a near-fieldexposure is intended to have a high aspect ratio by a resist layerhaving a double-layer stack structure, oxygen plasma etching isperformed, with the pattern 16 a being used as a mask. Examples ofoxygen-containing gases that can be used in the oxygen plasma etchinginclude oxygen, a mixed gas of oxygen and an inert gas such as argongas, or a mixed gas of oxygen and carbon monoxide, carbon dioxide,ammonia, dinitrogen monoxide, sulfur dioxide, or the like.

When the resist pattern 16 a formed through a near-field exposure isintended to have a high aspect ratio by a resist layer having athree-layer stack structure, etching is performed on the oxygen plasmaetching endurance layer, with the pattern 16 a being used as a mask. Wetetching or dry etching may be performed as the etching. However, dryetching is more suitable for forming fine patterns, and therefore, ismore preferable.

As the wet etching agent, a hydrofluoric acid solution, an ammoniumfluoride aqueous solution, a phosphoric acid aqueous solution, an aceticacid aqueous solution, a nitric acid aqueous solution, a cerium ammoniumnitrate aqueous solution, or the like can be used, depending on theobject to be etched.

Examples of gases for the dry etching include CHF₃, CF₄, C₂F₆, CF₆,CCl₄, BCl₃, Cl₂, HCl, H₂, and Ar, and a combination of some of thosegases can be used as needed.

After the etching of the oxygen plasma etching endurance layer, oxygenplasma etching is performed in the same manner as in the case of aresist layer having a double-layer stack structure, and the pattern istransferred to the lower resist layer 15.

By using the device manufacturing method according to this embodiment,the following devices or elements (1) through (6) can be manufactured:

(1) a semiconductor device;

(2) a quantum dot laser element having a structure in which GaAs quantumdots of 50 nm in size are two-dimensionally arranged at 50-nm intervals;

(3) a subwavelength structure (SWS) in which conical SiO₂ members of 50nm in size are two-dimensionally arranged at 50-nm intervals on a SiO₂substrate, and a light reflection preventing function is provided;

(4) a photonic crystal optical device or a plasmon optical device havinga structure in which 100-nm members made of GaN or a metal aretwo-dimensionally and periodically arranged at 100-nm intervals;

(5) a biosensor element or a micro total analysis system (μTAS) elementthat has a structure in which Au fine particles of 50 nm in size aretwo-dimensionally arranged at 50-nm intervals on a plastic substrate,and uses local plasmon resonance (LPR) or surface-enhanced Ramanspectroscopy (SERS); and

(6) a nanoelectromechanical system (NEMS) element such as a SPM probehaving a sharp structure that is used in scanning probe microscopes(SPM) such as a tunnel microscope, an atomic force microscope, and anear-field optical microscope, and are of 50 nm or less in size.

Example

The following is a description of an example of the twelfth embodiment.

A to-be-processed substrate having a light-curable resin applied theretois placed on the side of a near-field light generating film pattern of anear-field exposure mask. The to-be-processed substrate 12 used here isa silicon substrate. As the light-curable resin, a resin of Toyo GoseiCo., Ltd. is used.

A 1.5-μm infrared laser is used as the light source for the near-fieldexposure. The illumination intensity is approximately 85 mJ/cm² in thei-ray on the upper surface of the mask.

A line-and-space pattern of 20 nm in half pitch and approximately 100 nmin depth is obtained where the exposure time is two minutes, and aline-and-space pattern of 50 nm in half pitch and approximately 100 nmin depth is obtained when the exposure time was one minute.

Thirteenth Embodiment

Referring now to FIGS. 17A through 18C, a pattern forming methodaccording to a thirteenth embodiment is described. The pattern formingmethod according to the thirteenth embodiment is a method using ananoimprint method in which a pressing position is controlled.

First, as shown in FIGS. 17A and 17B, a Si substrate 80 is prepared, anda light-curable resin film 82 is formed on the Si substrate 80. Thelight-curable resin film 82 may be formed by a spinner technique, forexample. By the spinner technique, the number of rotations of thespinner is controlled by taking into account the viscosity and solidcontent of the light-curable resin film 82, and the evaporation rate ofthe solvent. In this manner, a desired film thickness can be obtained.After the formation of the light-curable resin film 82, prebake can beperformed to remove the solvent contained in the film.

As shown in FIG. 17C, a template 90 having a near-field light generatingfilm pattern 94 formed on a Si substrate 92 is prepared. This template90 can be a near-field exposure mask according to any of the firstthrough eighths embodiments. The light-curable resin film 82 formed onthe Si substrate 80 is then brought into contact with the near-fieldlight generating film pattern 94 of the template 90 (FIG. 17D).

With the light-curable resin film 82 and the near-field light generatingfilm pattern 94 being in contact with each other, light is emitted ontothe back surface side of the silicon substrate 80 or the opposite sidefrom the side on which the light-curable resin film 82 is formed, asshown in FIG. 17E. The light irradiation is performed for 0.1 to 20seconds. As a result, near-field light is generated at the edge portionsof the near-field light generating film pattern 94 of the template 90,and the generated near-field light reaches the light-curable resin film82. Since the light emitted in this embodiment is so-called nonresonantlight, the light-curable resin film 82 reacts directly to the emittedlight, but is not chemically changed at all when the irradiation timeand intensity are adjusted. In the step illustrated in FIG. 17D, thedistance between the Si substrate 80 having the light-curable resin film82 applied thereto and the template 90 can be determined based on thewavelength of the emitted light. In this embodiment, the template 90 isa template having the near-field light generating film pattern 94 formedon the Si substrate 92. However, the template 90 can be a concave-convexmold, and the material of the concave-convex mold can be Si.

The light intensity of the near-field light is higher at the concave andconvex edge portions that correspond to the pattern 94 of the template90. The light-curable resin film 82 reacts to the generated near-fieldlight due to the near-field light generated. As a result, thelight-curable resin film 82 is cured at local regions 82 a correspondingto the above-mentioned edge portions, as shown in FIG. 18A.

As shown in FIG. 18B, the template 90 is detached from the Si substrate80. Edge neighborhood portions 82 a formed by curing the light-curableresin film 82 with the near-field light generated in the stepillustrated in FIG. 17E and the light-curable resin film portions 82 b,in which no near-field light is generated and which are located outsidethe edge neighborhood portions 82 a, remain on the Si substrate 80.

The light-curable resin film portions 82 b remaining on the Si substrate80 is used as a mask, and etching is performed on the Si substrate 80.In this manner, a silicon substrate 80 a having a fine pattern can beobtained (FIG. 18C).

The near-field light generating film pattern 94 of the template 90 ismade of a metal containing at least one element selected from the groupconsisting of Au, Al, Ag, Cu, and Cr, and the film thickness of thepattern 94 may be greater than 0 nm and not greater than 40 nm. Thelight to be emitted can have a wavelength of 0.36 μm to 5.0 μm. Further,light can be emitted onto the template 90. The light-curable resin film82 may be formed so that it is not cured by light having a wavelength of1 μm to 5.0 μm.

The concave edge portions of the concave-convex mold serve as an evenfiner pattern. That is, by the nanoimprint method to which thisembodiment is applied, the light-curable resin film can be locally curedby near-field light rapidly enhanced at the concave and convex edgeportions, to form a sharp detachment face at the time of detachment. Inthis manner, a much finer pattern than a pattern formed with concavitiesand convexities can be formed. At the concave and convex edge portions,sharper electrical field gradients exist, depending on emitted light.However, a diabatic process that reacts only in those regions can beused. Accordingly, fine patterning of 10 nm or smaller can be performedwith high precision.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fail within thescope and spirit of the inventions.

1-11. (canceled)
 2. A pattern forming method for forming a pattern usinga near-field exposure mask, the pattern forming method comprising:forming a resist layer on a substrate; preparing a near-field exposuremask, in which a near-field light generating film pattern is formed on asilicon substrate; positioning the near-field exposure mask so that thenear-field light generating film pattern is in contact with a surface ofthe resist layer; injecting light to a side of the silicon substrate;causing the resist layer to react to near-field light generated from thenear-field light generating film pattern to generate first portions ofthe resist layer in which the near-field light is generated and secondportions of the resist layer in which no near-field light is generated,the near-field light being generated by the injected light; detachingthe near-field exposure mask from the silicon substrate; removing thefirst portions of the resist layer and remaining the second portions ofthe resist layer on the silicon substrate; and etching the siliconsubstrate using the second portions of the resist layer.
 13. The methodaccording to claim 12, wherein the light has a wavelength of 1100 nm ormore.
 14. The method according to claim 12, wherein the light isp-polarized.
 15. The method according to claim 12, wherein the light isinjected with a diagonal angle.
 16. The method according to claim 12,wherein the near-field light generating film is a film containing atleast one element selected from the group consisting of Au, Al, Ag, Cu,Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formedwith layers made of some of those materials.
 17. The method according toclaim 12, wherein the near-field light generating pattern has theconvexities.
 18. The method according to claim 17, wherein a height ofat least one of the convexities in the near-field light generatingpattern is 50 nm or less.
 19. A pattern forming method for forming apattern using a near-field exposure mask, the pattern forming methodcomprising: forming a resist layer on a substrate; forming alight-curable resin on the resist layer; preparing a near-field exposuremask, in which a near-field light generating film pattern is formed on asilicon substrate; positioning the near-field exposure mask so that thenear-field light generating film pattern is in contact with a surface ofthe light-curable resist layer; injecting light to a side of the siliconsubstrate; causing the light-curable resist layer to react to near-fieldlight generated from the near-field light generating film pattern togenerate first portions of the curable-light resist layer in which thenear-field light is generated and second portions of the light-curableresist layer in which no near-field light is generated, the near-fieldlight being generated by the injected light; detaching the near-fieldexposure mask from the substrate; removing the first portions of thelight-curable resist layer and remaining the second portions of thelight-curable resist layer on the substrate; patterning the resist layerusing the second portions of the light-curable resist layer to form apattern of the resist layer; and etching the substrate using the secondportions of the light-curable resist layer and the pattern of the resistlayer.
 20. The method according to claim 19, wherein the light has awavelength of 1100 nm or more.
 21. The method according to claim 19,wherein the light is p-polarized.
 22. The method according to claim 19,wherein the light is injected with a diagonal angle.
 23. The methodaccording to claim 19, wherein the patterning of the resist layer isperformed with oxygen plasma etching.
 24. The method according to claim19, wherein the near-field light generating film is a film containing atleast one element selected from the group consisting of Au, Al, Ag, Cu,Cr, Sb, W, Ni, In, Ge, Sn, Pb, Zn, Pd, and C, or a film stack formedwith layers made of some of those materials.
 25. The method according toclaim 19, wherein the near-field light generating pattern has theconvexities.
 26. The method according to claim 25, wherein a height ofat least one of the convexities in the near-field light generatingpattern is 50 nm or less.